From
the Global Warming Sceptics:

So You Think Greenland Used to
be Green ?

Some Think: Greenland used to be a lovely
hospitable island when the Vikings settled it. It was not until the
Little Ice Age that it got so cold and it was clearly not the frozen
wasteland it is today.

A
bit of urban myth here, I’ll just try to correct the record
and mention how a regional anecdote is not evidence of global
anything.

Answer:

Firstly, Greenland is just a
part of a single region and as such can not be assumed to represent
any kind of global climate shift.

Secondly, a quick reality check
shows that Greenland's ice cap is hundreds of thousands of years old
and covers 95% of that island, so just how different could it have
been only 1000 years ago?